Flame resistant fabrics having high resistance to pilling, and methods of making same

ABSTRACT

A flame resistant fabric having a high level of pilling resistance and good strength characteristics is described. In addition, a method of making the fabric is also described.

BACKGROUND OF THE INVENTION

Fire resistant fabrics are used in a variety of products, such as apparel for firemen and electrical workers, military flight suits, and the like. Such fabrics are commonly made from aramid fibers, which are high strength fibers that have inherent flame resistant (“FR”) properties. While performing well in many respects, aramid fibers have several disadvantages. For one, they are very expensive. Secondly, because of the aramid fiber strength, fabrics made from those fibers have a high propensity to pill. As will be readily appreciated by those of ordinary skill in the art, “pilling” is “the tendency of fibers to work loose from a fabric surface and form balled or matted particles of fiber that remain attached to the surface of the fabric.” (Dictionary of Fiber & Textile Technology, p. 113, copyright 1989, Hoechst Celanese.) Pilling is aesthetically undesirable, both from a look and feel standpoint, and is a common reason for garment retirement. Pilling tends to get worse after wearing and laundering of a garment. Therefore, the pilling propensity of the aramid fabrics can lead to an undesirably shortened life cycle for products made from these fabrics.

SUMMARY

The present invention achieves aramid fabrics having pilling resistance levels that were not previously achievable on conventional aramid fabrics. The invention involves producing a fabric from specially spun aramid yarns, then treating the fabric with a special chemical lubricant. The resulting fabrics have high degrees of pilling resistance, while maintaining all of the aesthetic and performance features of their conventional counterparts.

DETAILED DESCRIPTION

In the following detailed description of the invention, specific preferred embodiments of the invention are described to enable a full and complete understanding of the invention. It will be recognized that it is not intended to limit the invention to the particular preferred embodiment described, and although specific terms are employed in describing the invention, such terms are used in a descriptive sense for the purpose of illustration and not for the purpose of limitation.

The fabrics of the invention are desirably manufactured from vortex spun yarns, such as those manufactured by the method developed by the Murata company of Japan, and known as Murata Vortex Spun (“MVS”) yarns. The yarns are selected to be of a size that will enable the achievement of a desired weight of fabric. The weight can be selected for the desired end use, and in the case of apparel, will desirably range from about 2 to about 10 oz/sq yard, or in the case of a flight jacket fabric, will desirably be about 4 to about 5 oz/sq yard, and more preferably, about 4.4 to about 4.6 oz/sq yard.

The yarns are formed into a fabric using a conventional fabric formation method such as weaving. The fabric can be of any construction, including but not limited to a plain weave, twill weave, satin weave, oxford weave, or the like.

The spun yarns are desirably made from a majority of aramid fibers having inherent FR properties, such as those marketed under the tradename Nomex by E. I. duPont de Nemours and Company of Wilmington, Del. However, the yarns may also include some quantity of other fibers, such as other aramid fibers, nylon, FR rayon, etc. For example, one blend that has been found to perform well in the invention is known commercially as Nomex IIIA®, which includes a blend of Nomex® FR aramid fibers, Kevlar® aramid fibers, and P-140 nylon fibers. Preferably, the yarns include at least about 90% of FR aramid fibers.

As noted previously, the fibers are desirably vortex spun. One company identified as having vortex spinning capability is Pharr Yarns of McAdenville, N.C. The fabric is desirably made substantially entirely from the vortex spun yarns.

However, it was found that when fabrics were woven from vortex spun yarns and treated with the conventional chemistry used on the current products (made from ring spun yarns), the strength characteristics were significantly lower than those of the fabrics made from the ring spun yarns (and too low for certain end uses.) However, it was surprisingly found that with the application of a particular lubricant, strength levels and hand levels approximating those of the fabrics made from ring spun yarns could be achieved.

The fabric also desirably contains about 0.25-3% of a high molecular weight ethoxylated polyester lubricant (on weight of fabric.) The lubricant can be added at any point in the manufacturing process. For example, in one method of the invention, the fabric is woven, then prepared (i.e. washed) in a conventional manner, then dried, also in a conventional manner. The fabric is then desirably passed through a chemical bath containing lubricant, and other chemicals as may be desired (e.g. flame retardants, repellents, soil release agents, sewing lubricants, etc.) In this embodiment of the invention, the fabric desirably achieves about 80% initial wet pick up, which is reduced by passage over a vacuum slot to about 35% wet pick up. The fabric is then dried and taken up, and it has about 0.25 to about 3% lubricant on the fabric.

The lubricant is preferably in the form of a high molecular weight ethoxylated polyester; however, other types of lubricants may also be used within the scope of the invention, provided that they achieve the requisite aesthetic and performance characteristics.

EXAMPLES Example A

A conventional FR aramid fabric of the variety conventionally used to produce military flight suits was produced. Specifically, a fabric was woven in a plain weave construction in a conventional manner, using 39.8/2 ring spun yarns of Nomex IIIA (92% Nomex FR aramid fiber, 5% Kevlar® fiber, and 3% P-140 nylon fiber, commercially available as Nomex IIIA® from E. I. duPont de Nemours and Co. of Wilmington, Del.) in each of the warp and the filling directions. The fibers had been dyed during the fiber manufacturing process. The fabrics were then prepared and dried in a conventional manner, and passed through a chemical bath of 1.0% flame retardant (Antiblaze NT, commercially available from Rhodia, Inc. of Cranbury, N.J.) and 1.0% high density polyethylene emulsion sewing lubricant (Atebin 1062, commercially available from Boehme Filatex of Reidsville, N.C.). Concentrations were based on concentration of bath at about 80% wet pick up, which was reduced to 35% wet pick up via passage over a vacuum slot. The fabric was then dried in a conventional manner and taken up. The fabric had a finished weight of 4.35 oz/sq yard, and 70 ends per inch and 49 picks per inch.

Example B

A fabric was woven in a plain weave construction, using 39.8/2 Murata Jet Spun (“MJS”) yarns of Nomex IIIA in the warp and filling directions. The fabric was then prepared and dried in a conventional manner, and passed through a chemical bath containing 1.0% flame retardant (Antiblaze NT) and 1.0% sewing lubricant (Atebin 1062). Concentrations were based on concentration of bath at about 80% wet pick up, which was reduced to 35% wet pick up via passage over a vacuum slot. The fabric was then dried in a conventional manner. The fabric had a finished weight of 4.40 oz/sq yard, and 70 ends per inch and 50 picks per inch.

Example C

A fabric was woven in a plain weave construction, using 39.8/2 Murata Vortex Spun (“MVS”) yarns of Nomex IIIA in the warp and filling directions. The fabric was then prepared and dried in a conventional manner, then passed through a chemical bath including the following: 1.0% flame retardant (Antiblaze NT), 1.0% sewing lubricant (Atebin 1062), and 1.0% high molecular weight ethoxylated polyester (Lubril QCX from Tennessee Eastman) at a wet pick up of about 80%, which was reduced to 35% wet pick up via passage over a vacuum slot. The fabric had a finished weight of 4.37 oz/sq yard, and 70 ends per inch and 49 picks per inch.

TEST METHODS

-   Tensile Strength—Tensile strength in each of the warp and filling     directions was tested for each of the samples according to ASTM     D5035-1995. A typical specification for a military flight suit     fabric would require 180 lbs in the warp and 100 lbs in the filling. -   Tear Strenqth—Tear strength in each of the warp and fitting     directions was tested for each of the samples according to ASTM     D1424-1996. A typical specification for a military flight suit     fabric would require 12 lbs in the warp and 8 lbs in the filling. -   Abrasion—Abrasion resistance was tested in each of the warp and     filling directions using a Wyzenbeck abrasion tester according to     ASTM D4157-1992. -   Pilling—Pilling was tested at 30, 60 and 90 minutes according to     ASTM D3512-2002. -   Air Permeability—Air permeability was tested according to ASTM     D737-1996. -   Drape—Drape was tested according to the following procedure, using a     FRL® Drapemeter (produced by Fabric Research Laboratories of Dedham,     Mass.) The test is designed to determine the extent to which a     fabric will deform when allowed to hang under its own weight, or the     ability of the fabric to drape by orienting itself into folds or     pleats when acted upon by the force of gravity. In addition to the     Drapemeter, a uniform grade of tracing paper, balance, and scissors     are used. The test specimens and tracing paper are conditioned to     equilibrium and tested in the standard atmosphere of 65% relative     humidity and 70° F. Moisture equilibrium is approached from the dry     side (not moisture free.) Six test specimens (3 face up, and 3 face     down), 10 inches in diameter are cut from the fabric to be tested.     The specimens taken from the right, center and left fabric areas,     but no closer to the selvage than {fraction (1/10)} of the fabric     width. The specimens are marked as to face and back. A 10 inch     diameter circle is cut from a uniform grade of tracing paper and     weighed to the nearest milligram. This weight is recorded as W1. A     40-inch diameter circle (to represent the annular support ring) is     cut and weighed to the nearest milligram. This is recorded as W2.     Take a 10 inch diameter specimen and make a hole marking the center     of the test specimen. Place the specimen on the support ring,     centering the specimen on the support. Next, place a sheet of     tracing paper on the clear top side of the Drapemeter. With the     light source on, center the paper about the projected image of the     fabric specimen and carefully trace the outline of the shadow image     on the paper. Cut out the traced image and weight the image paper to     the nearest milligram. Record as W3. Calculate Drape Coefficient as     (W3-W2)/(W1-W2)×100, where W1 is weight, 10 inch diameter paper,     mg., W2 is weight of 4 inch diameter paper, mg., and W3 is weight,     projected image, cut from paper used to obtain W1, mg. Report the     average of the six readings as the Drape Coefficient -   Handle—Handle was tested using a Handle-o-meter according to INDA     (Association of the Nonwoven Fabrics Industry, Cary, N.C.) Standard     Test IST 90.3 (1995). -   Fraying—Fraying was tested in each of the warp and filling     directions according to the following Circular Test Method. Sample     preparation: Cut five circular pieces of fabric having a 5+/−0.001     inch diameter. Mark the warp direction. Procedure: Measure the     diameter on each specimen and record as the original diameter.     Identify each specimen in an area that will not be lost during the     test (near the center.) Place all 5 circles in a Random Tumble     chamber and run for 10 minutes. Remove from the Random Tumble     chamber and measure the diameter of the fabric in both the warp and     filling direction (measure only the woven fabric.) In cases where     the entire yarn was not removed, measure the shortest distance.     Calculations: The results identify the loss of fabric as measured in     the direction of interest. Example: a 10% warp means that 90% of the     original fabric remains as measured in the warp direction. A loss of     fabric as measured in the warp direction means the filling yarn is     fraying out of the fabric. Loss of fabric in measured     direction=A-B/A*100, where A=original diameter and B=after fraying     diameter. -   Load—Load was tested using a Ring Load test according to the     following method Scope: Fabric is pulled through a ring at a set     rate to determine the forces associated with friction and bending.     Procedure: Cut a 10-inch diameter circle of fabric to be tested.     Mark the center of the circle. Set up the tensile tester with 38 mm     diameter ring with a radius of 24 mm. Test speed is 10 inches/min.     Attach a string to a small fishhook, with barb removed, to the     center of the fabric. Attach the other end of the string to the     crosshead of the tensile tester. Start the tester and run until the     fabric has been pulled completely through the ring. Record the force     required to pull the fabric through the ring and the modulus of the     initial folding of the fabric as it approaches the ring. -   Seam Slippage—Seam slippage was tested in each of the warp and     filling directions according to ASTM D4034-1992. -   Moisture Transport—Moisture transport was tested after 5 washes     according to the following Test Method (modified version of AATCC     Test Method 39-1980.) Purpose and scope: This test is for the quick     evaluation of wettability. Principle: A drop of water is allowed to     fall from a given height onto the surface of a taut test specimen.     The time required for the water drop to be completely absorbed by     the fabric is measured and recorded. Apparatus and materials:     Straight medicine dropper delivering 15 to 25 drops per milliliter,     stop watch or equivalent timer, distilled or demineralized water,     embroidery hoop. Test specimens: Fabric specimens should be allowed     to reach equilibrium with the environment of the testing area. A     sample large enough to test 3 samples was used. The sample was     washed 5 times at 140° under ordinary home wash conditions. The     fabric sample to be tested is positioned within an embroidery loop     (without tension). The dropper is held 3 inches above the fabric     surface and one drop of water is dropped onto the fabric surface.     The time for the drop to be completely absorbed is recorded. Three     tests were conducted for each fabric sample and the results were     averaged. -   Soil Realease—Soil release was tested for corn oil and mineral oil     according to AATCC 130-1995 Test Method as follows: stained at 0     washes, measured after one wash, stained at 4 washes, measured after     5 washes, and stained at 9 washes, measured after 10 washes.     According to the test methods, the samples are visually rated on a     scale of 1-5, with a typical military flight suit specification     requiring a 3 rating to pass. -   Flammability—After flame, After glow, char length and break open     were all tested according to Fed. Mtd. 5930 (1978) Test Method. -   Electrostatic Decay—Electrostatic decay was tested according to Fed.     101 C Mtd. 4046 (1982) Test Method. -   Weight—Weight was measured in accordance with ASTM D3776, Option     C-1996.

pH—pH was measured according to ASTM D2165-1994. Test Example A Example B Example C Tensile-warp (lbs) 210 177 198 Tensile-filling 132 120 127 (lbs) Tear-warp (lbs) 16.9 13.5 14.3 Tear-filling (lbs) 14.7 11.5 13.5 Abrasion-warp 90000 not tested 90000 (cycles) Abrasion-filling 68398 not tested 65493 (cycles) Pilling-30 minutes 3.5 3.5 4.0 Pilling-60 minutes 3.0 3.0 3.5 Pilling-90 minutes 1.4 2.0 3.0 Air Permeability 93 100 99 (cubic feet/minute) Drape (%) 39 not tested 35 Handle-O-Meter - 32 not tested 35 warp (grams) Handle-O-Meter - 33 not tested 32 filling (grams) Fraying-warp (%) 15 not tested 18 Fraying-filling (%) 19 not tested 20 Ring Load Test 134.5 not tested 130.7 (grams) Seam slippage- 30 not tested 47 warp (lbs) Seam slippage- 54 not tested 56 filling (lbs) Moisture 1.3 not tested 1.6 Transport-5 washes (secs) Soil Release 0/1- 3.8 not tested 3.5 corn oil (rating) Soil Release 4/5- 4.9 not tested 3.8 corn oil (rating) Soil Release 9/10- 4.1 not tested 4.8 corn oil (rating) Soil Release 0/1- 3.7 not tested 3.1 mineral oil (rating) Soil Release 4/5- 4.3 not tested 3.4 mineral oil (rating) Soil Release 9/10- 4.2 not tested 3.8 mineral oil (rating) Flammability- 0.0 0.0 0.0 After Flame (secs) Flammability- 0.0 0.0 0.0 After Glow (secs) Flammability- 2.6 2.6 2.6 Char Length (inches) Flammability- Pass Pass Pass Break Open Electrostatic Pass Pass Pass Decay Fabrics from Examples A and C were then taken following weaving, and treated as follows (percentages in the chemical baths are on weight of bath): A1 and C1 were prepared in a conventional manner and dried. The fabrics were then passed through a chemical bath including the following: 1.0% flame retardant (Antiblaze NT, commercially available from Rhodia, Inc. of Cranbury, N.J. and 1.0% sewing lubricant (Atebin 1062, commercially available from Boehme Filatex of Reidsville, N.C., at a wet pick up of about 80%, which was reduced to a wet pick up of 35% via passage over a vacuum slot. The fabrics were then dried in a conventional manner, and taken up. A2 and C2 were prepared in a conventional manner and dried. The fabrics were then passed through a chemical bath including the following: 1.0% flame retardant (Antiblaze NT) and 2.0% sewing lubricant (Atebin 1062), at a wet pick up of about 80%, which was reduced to a wet pick up of 35% via passage over a vacuum slot. The fabrics were then dried in a conventional manner and taken up. A3 and C3 were prepared in a conventional manner and dried. The fabrics were then passed through a chemical bath including the following: 1.0% flame retardant (Antiblaze NT), and 3.0% sewing lubricant (Atebin 1062), at a wet pick up of about 80%, which was reduced to a wet pick up of 35% via passage over a vacuum slot. The fabrics were then dried in a conventional manner and taken up. The fabrics had a high tendency to fray. A4 and C4 were prepared in a conventional manner and dried. The fabrics were then passed through a chemical bath including the following: 1.0% flame retardant (Antiblaze NT), 1.0% sewing lubricant (Atebin 1062), and 1.0% high molecular weight ethoxylated polyester (Lubril QCX from Tennessee Eastman) at a wet pick up of about 80%, which was reduced to a wet pick up of 35% via passage over a vacuum slot. The fabrics were then dried in a conventional manner and taken up.

The fabrics were tested according to the same methods described above, and the results are listed in the table below. Tear-filling Tensile-warp Tensile-filling Sample Tear-warp (lbs) (lbs) (lbs) (lbs) A1 15.13 10.27 212.1 128.9 A2 14.00 10.84 211.5 129.7 A3 15.39 10.70 209.6 121.2 A4 15.55 11.61 200.7 122.3 C1 10.41 9.38 189.4 127.7 C2 12.24 9.66 177.3 127.6 C3 12.43 9.66 184.3 128.0 C4 13.65 10.27 191.3 123.5

As illustrated, the fabric of the invention had good FR performance and aesthetic characteristics at a high level of strength. While particularly described in connection with the manufacture of apparel, it is noted that the fabrics can be used in any other end use where FR and fabric strength characteristics are desired and pilling is considered to undesirable, including but not limited to all forms of apparel (shirts, jackets, hats, gloves, pants, shorts, coveralls, etc.), upholstery, etc.

The fabrics of the invention desirably have good FR characteristics, as evidenced by a char length of about 4 inches or less when tested according to Fed. Mtd. 5930 (1978) Test Method, and a pilling of greater than 2 after 90 minutes when tested according to ASTM D3512-2002, and even more preferably about 2.5 or greater, and even more preferably, about 3. In addition, the fabrics desirably having a pilling rating of greater than 3 after 60 minutes, and a pilling rating of greater than 3.5 after 30 minutes.

In the specification there has been set forth a preferred embodiment of the invention, and although specific terms are employed, they are used in a generic and descriptive sense only and not for purpose of limitation, the scope of the invention being defined in the claims. 

1. A method of making a fabric having good flame resistance and strength and low pilling characteristics comprising the steps of: a) providing a plurality of vortex spun yarns comprising at least about 90% flame resistant aramid fibers, b) forming a fabric from said vortex spun yarns, and c) providing a lubricant on said yarns, such that said fabric has an overall concentration of about 0.25% to about 3% lubricant on weight of fabric.
 2. The method of claim 1, wherein said step of forming a fabric comprises weaving.
 3. The method of claim 1, wherein said step of providing a lubricant comprises treating the yarns, prior to or subsequent to step b), with a high molecular weight ethoxylated polyester.
 4. A method of making a fabric having good flame resistance and strength and low pilling characteristics comprising the steps of: a) providing a plurality of vortex spun yarns comprising at least about 90% flame resistant aramid fibers, b) forming a fabric from said vortex spun yarns, and c) providing a lubricant on said yarns, to thereby achieve a fabric having a char length of less than about 4 inches when tested according to Fed. Mtd. 5930 (1978) Test Method, and a pilling of about 2 or greater when tested according to ASTM D3512-2002 after 90 minutes.
 5. The method of claim 4, wherein said step of providing a lubricant comprises providing a high molecular weight ethoxylated polyester to said yarns.
 6. A flame and pill resistant fabric comprising: a woven fabric comprising spun yarns comprising at least about 90% flame resistant aramid fibers, wherein said fabric has a pill resistance of greater than 2 after 90 minutes when tested according to ASTM D3512-2002.
 7. The fabric according to claim 6, wherein said spun yarns comprise vortex spun yarns.
 8. The fabric according to claim 6, wherein said fabric has a pill resistance of about 2.5 or greater after 90 minutes.
 9. The fabric according to claim 6, wherein said fabric comprises at least about 0.25% on weight of fabric of a high molecular weight etholxylated polyester lubricant.
 10. A flame and pilling resistant fabric comprising: a woven fabric comprising vortex spun yarns containing at least about 90% flame resistant aramid fibers and at least about 0.25% of a high molecular weight ethoxylated polyester lubricant provided on said fabric.
 11. The fabric according to claim 10, wherein said fabric has a pilling resistance greater than 2 after 90 minutes when tested according to ASTM D3512-2002. 